I havent gotten 3 displays to work yet with Windows, although some others have. As far as running Integraded Video + Video Card, I haven't had this work yet with PCI Express Video Cards and Integrated Video, however I was able to make it work with a older GeForce 4 MX 440 PCI video card in a HP Pentium 4 running Windows XP Pro SP2 where I was able to set up dual-displays and span the content among the 2 displays among the Geforce Video card and Intel 845 chipset GPU.
All systems with AGP or PCI Express, the motherboards for me took it as default to disable the integrated and not offer it to be enabled. It may be a feature that is hard coded into the motherboards design that may allow for you to run both integrated and a card in AGP or PCIe slot at same time for multiple displays, but the only setup that I found that worked for multiple displays with integrated used along side a video card was with an older Pentium 4 HP S-Class tower with older PCI video card.
These days people who use multiple displays generally have a video card with 2 outputs or motherboard that allows for 2 video cards to have say 4 display outputs etc, however there is also a method I have seen for a point of sale application where they wanted to add a display to a setup that wouldnt take a video card installation and so they added a USB/VGA video card adapter, which while its not powerful enough for video content or gaming, it allows for information to be displayed and runs off of an available USB port and monitor connected with it. The OS treats it as an extra video card even though its a USB video card device that is not very powerful for processing thru its small lightweight processing GPU. We used a product like this one, but not this same model. I think ours was made by Startech:
http://www.newegg.com/Product/Product.aspx?Item=N82E16812866007 * Not sure if this device is hard coded to only act as display #2 or if you can team it with a video card that has 2 video outputs and use it as a 3rd, but you can always contact the mfr before buying it to see if they claim it will work as a 3rd display adapter.
In the stores that we used these USB VGA video adapters in we basically had a small 15" flat screen display at the registers that ran through a powerpoint slide loop to advertise to the customers while they were standing in line about store events that were coming up such as Wine Tasting on Friday at 6pm, or other promotional stuff to drive sales or show a short series of information on the community charity "partner of the month" that customers can donate $1, $5, $10, or $20 to by grabbing colored slips of paper and handing them to the cashier to scan the barcode on and donate money to a charity etc.
These worked well for the stores application and are probably still working 5 years later, BUT... were only set up as 2nd displays vs 3rds!